how to: reverse output I/S fuel sender

[tank_post142]

1st pic is stock sending unit, float is on rt side of tank, reads 0 ohms full, 90 ohms empty.



take the sending unit and bend the rod 90 degrees, so the resistor is now pointing to the rear
mount unit into tank with arm now in the left side of tank. it now reads 90 ohms full, 0 ohms empty.
you can get fuel gauges all day long in this configuration.

[John Schmidt]

Tank, maybe it's my older eyes but it looks like it's unchanged to me.  Your pictures are laid out the exact opposite, maybe that's why it looks that way. How about taking a before and after shot with everything laid out the same, that should show how the arm was bent. As for me, I reversed the wire connections by unsoldering and resoldering them at the base of the swing arm by the resistor. I haven't tried it installed, but a digital meter shows the readings reversed when you move the arm up/down.

[BonS]

This is a great subject! I've been running with my gas gauge reading backwards and I'm almost used to it. It might discourage a thief!

John, reversing the resistor leads won't reverse the 90-0 to a 0-90 though.  Unless the resistor has a (three wire) connection to its opposite end you can't reverse the readings electrically by reversing the two wires.

On the other hand bending the float to work upside down has it problems if the float is move backward in the tank. The resistor used in the sender is carefully engineered (non-linear) to give an accurate reading given the highly irregular shape of the IS tank. Moving the float to a more rearward position will distort the readings. I may be better than a backward reading though.

Though I believe it's now discontinued, VDO made the model 301-509 gas gauge that reads correctly for our sender. You may be able to find one lingering somewhere. They come up in a Google search.

Tank, I too am struggling to visualize your mod. Can you clarify where the bend was reversed and the location of the float afterwards relative to the original position? Thanks!

[tank_post142]

ok, lets give this a try for our "spatially challenged" friends:
NOTE: ALL PICS ARE TAKEN WITH THE FLOAT IN THE 90 OHM POSITION
the first picture shows the float assy in it's original position in relation to the fuel tank:



the second picture show the new position of the float, once we twist the arm that mounts it to the base:


now when we install the unit we will be installing it "backwards" the float arm originally was in the right 1/2 of the tank (full was up and forward) now we will install it so the arm is in the left 1/2 of the tank(full will be up and forward)



please note that the drawing of the tank reflects left and right sides of the tank. as you can see, the float still moves from up and forward (full) to straight down(empty) but it will now send 90 Ohms at full and 0 Ohms at empty. the float arm will probably have to be tweeked around slightly to get a perfect read on the gauge.

[MP]

I put a Motosen gauge on mine.  They make the gauge right to the sender.  I have noticed some other gauges too, where you specify which way you want the gauge to read.  If it was me, I would just order the correct gauge to start with.

MP

[tank_post142]

i can purchase a full set of good looking conventional gauges for about the price of a motosens fuel gauge.

[BonS]

Thanks, Tank, for your detailed reply. I understand what you have done now and admire your ingenuity. That said, I believe that the gauge readings will be distorted by the inversion of the sender. Full will read full and empty is empty but the readings in between will not be accurate due to the non-linear nature of the thick film resistor designed by mother Honda to account for the irregular tank shape. I would have gone with a Motosen fuel gauge but they don't make a boost gauge. So this is what I ended up with: Motosen engine temp, voltage and clock and AutoMeter fuel and boost gauges.


Someday I'll work on an electronic board to invert the signal from the sender to the fuel gauge but until then it'll be backward.

[John Schmidt]

Although I have experimented with a new sender I have on the shelf, I've had an Autometer C-2 series fuel gauge installed for probably 7 years now. I'd love to be able to find something in the automotive realm I could use from Autometer. What I really want to do is have just two large gauges; a speedo and a tach. And at the bottom of their face they have two smaller guages on each one that will give you temp, voltage, oil pressure, fuel. But until the sending unit can be converted to match the rest of the world, that's not going to happen. 

This is what I have now; fuel in the center, temp on the left and oil pressure on the right. Had them on there about 7 years or more with no trouble, just getting bored I guess.

[BonS]

So John, you're using the C-2 programmable fuel gauge? Did you do the custom programing method and it works well (90-0 ohms) with the IS fuel sender? It sounds like a pain in the neck to program but it is easier than making a custom electronic adapter for the wrong meter!

[tank_post142]

well, i just probed each of the 30 little contacts on the sender, each one reads 3.1 Ohms higher than the next. this means there is no custom resistance on the sending unit to compensate for tank shape.

[BonS]

  That's great news! I'm amazed but the truth is in the measurements. Are the contacts spaced evenly apart? I'm trying to figure out why they went to all that trouble with the zig-zags. I don't have one to look at but with what you're saying I'll soon be pulling mine out and going to the left side.

[John Schmidt]

So John, you're using the C-2 programmable fuel gauge? Did you do the custom programing method and it works well (90-0 ohms) with the IS fuel sender? It sounds like a pain in the neck to program but it is easier than making a custom electronic adapter for the wrong meter!

Yes, the preprogrammed setups won't work with our sender so I used their custom programming. Really no big deal, just make sure the bike is upright when you do it or you'll get an erroneous reading. I have mine set so when the needle is on empty I still have slightly over a gallon left. I've found I have to go to reserve soon after hitting empty and it takes approx. 5.5-5.7 gallons on a 6.9 gallon tank. I have a Pingle manual petcock on which I extended the pickup tube to closely match the OEM petcock. Like I said earlier, it's been on there for over seven years with no trouble. And the blue lights are kinda neat at night. 

[John Schmidt]

So this is what I ended up with: Motosen engine temp, voltage and clock and AutoMeter fuel and boost gauges.


Someday I'll work on an electronic board to invert the signal from the sender to the fuel gauge but until then it'll be backward.

Is that a Honda or a Boeing?

Stu, as I recall I think BonS has a blower on his bike....er....rocket. 

[John Schmidt]

John, like we were talking on Saturday.  When I was bike shopping, there were a lot of bikes (Harley mostly) that had piles of extra chrome and items that didn't do much.   I like what Mr. BonS has done, as everything is useful.

I agree. Slapping on a bunch of bolt-on's a custom doesn't make. It appears he's done things with the same thought in mind that I use when adding something; I want it to be functional. I have a spare sending unit and had to pull it off the shelf and see what Tank was talking about. I now understand his approach and he's right....it reverses the movement of the wiper on the float arm. In doing so, it reverses the ohm reading. Now I have another problem....finding the gauge setup I want to convert to. I really wish I hadn't read the original post now.